Chapter Two - Test One Flashcards
Solar radiation accounts for more than ___ of the energy that heats the earth and its atmosphere
- This energy is not distributed evenly, however, as it varies by:
- 9%
- latitude; time of day; time of year.
- It is this uneven distribution of energy that creates most of what we consider to be weather.
Rotation:
earth rotates on its axis once per 24 hours
Revolution:
earth orbits around the sun once per 365.25 days per year
The Seasons
Regulated by the amount of solar radiation received by the surface of the Earth; which is dictated by:
1) angle at which the radiation strikes the surface:
2) length of the “day” (# of daylight hours)
radiation striking the earth perpendicularly is:
- much more intense than that striking at an angle (Fig 2.3)
- traverses through less atmosphere (Fig 2.4)
- length of days allow for more radiation to reach the earth’s surface (Table 2.2)
Equinox ~ 12 hours everywhere
Earth’s Orientation
- These changes are due to the Earth being tilted by 23.5º from the plane of its elliptical orbit around the sun (Fig 2.5)
- The Earth’s axis (center of rotation) points in the same direction into space all year long; as a result:
The NH: is tilted toward the sun in summer (northern hemisphere) is tilted away from the sun in winter
Solar Elevation Angle (Noontime)
Figure 2.6 and Box 2.2 (The Analemma) provide ways to calculate the solar elevation angle (β) at local noon for any latitude and time of year. This angle can also be calculated using the following equation:
β =90-Phi-(23.5ºxcos((360(N+10))/365))
where: Phi is the latitude
N is the Julian day of the year (N=1… 365)
Solar Radiation Equation - provides an instantaneous measure of the intensity of the solar radiation (Watts) per square meter (ignoring effects of atmosphere):
J = 1367 Watts/Meters^2 x sin β
Summer Solstice “Astronomical start of summer”
Sun is at its highest position in the sky, as a result, radiation shines down on the surface:
~June 21 : Julian Day 173
- more directly than at any other time of the year.
- Longest “day” of the year
Summer Solstice “Astronomical start of summer”
each latitude (in NH) will have:
- more than 12 hours of sunlight
- the farther north you go, the greater the # of daylight hours (Table 2.2) - from Arctic Circle (66.5o N) north, 24 hours of sunlight - The noon sun is directly overhead at 23.5ºN, the: Tropic of Cancer
Notice that the sun actually rises north of east and sets north of ____ during Summer Solstice
west
Winter Solstice “Astronomical start of winter”
Sun is at its lowest position in the sky, as a result, radiation shines down on the surface:
~ December 21 : Julian Day 356
- less directly than any other time of the year
- Shortest “day” of the year
- each latitude (in NH) will have less than 12 hours of sunlight
- the farther north you go, the
lesser the # of daylight hours - from Arctic Circle (66.5ºN)
north, 24 hours of darkness - The noon sun is directly
overhead at 23.5ºS, the: Tropic of Capricorn
Notice that the sun actually rises ____ of east and sets south of west during Winter Solstice
south
Autumnal Equinox “Astronomical start of autumn”
( ~ September 23 : Julian Day 266)
Vernal Equinox “Astronomical start of spring”
( ~ March 20 : Julian Day 80)
In an equinox, each latitude (NH and SH) will have:
Exactly 12 hours of sunlight and 12 hours night (hence the name equinox)
- The noon sun is directly overhead (90º from the horizon) at: 0.0º (Equator)
Energy:
the capacity to do work
Kinetic Energy (KE):
energy associated with an object by virtue of its motion; KE = ½ mv2
Potential Energy (PE):
energy associated with an object by virtue of its position with respect to gravity
PE = mgh
Temperature:
degree of hotness or coldness of an object
- is a form of Kinetic energy
- or a measure of the average speed of all of the atoms and molecules of that object
- As The Speed Increases, T Increases
- As the speed decreases, T decreases
